In an arrangement of said type, used e.g. in connection with portable liquid gas containers, the pressure fluid passage of the container spout, i.e. of the first coupling part, discharges through a bore, the diameter of which is only a little larger than the diameter of the portrusion of the second coupling part. An O-ring is provided to perform sealing around the protrusion in the assembled state of the coupling. For this purpose, it is a condition that the O-ring fits tightly around the protrusion. The O-ring will, thus, be exposed to a certain wear any time the protrusion is forced into and is pulled clear of the mouth of the container spout. The higher the fluid pressure which the O-ring is to seal against, the tighter the O-ring must fit about the protrusion, since the pressurized fluid seeks to leak through the joint between the annular gasket and the protrusion.